Experiments on: (a) the dependence of longevity (fruit flies, cockroaches) on "normal" circadian organization. The experiments ask if longevity is reduced by driving the insects (with light cycles) to 21 and 27 hour days (compared with 24 hour days); (b) the extent to which the properties of circadian "clocks" change with age (mice, fruit flies, cockroaches). BIBLIOGRAPHIC REFERENCE: C.S. Pittendrigh and S. Daan, "A Functional Analysis of Circadian Pacemakers in Nocturnal Rodents, In: Stability and Lability of Freerunning Frequency," J. Comp. Physiol. (in press) 1976.